1. Field of the Invention
The present invention relates generally to products and methods for the in vivo production of monatin sweetener. More specifically, the present invention relates to products and methods for the in vivo secretion of monatin sweetener.
2. Related Art
Monatin is a high-intensity sweetener having the chemical formula:

Monatin includes two chiral centers leading to four potential stereoisomeric configurations. The R,R configuration (the “R,R stereoisomer” or “R,R monatin”); the S,S configuration (the “S,S stereoisomer” or “S,S monatin”); the R,S configuration (the “R,S stereoisomer” or “R,S monatin”); and the S,R configuration (the “S,R stereoisomer” or “S,R monatin”). As used herein, unless stated otherwise, the term “monatin” is used to refer to compositions including all four stereoisomers of monatin, compositions including any combination of monatin stereoisomers, (e.g., a composition including only the R,R and S,S, stereoisomers of monatin), as well as a single isomeric form.
For purposes of this disclosure, the monatin carbon backbone will be numbered as illustrated above, with the carbon attached to the alcohol group being identified as the 2-position carbon and the carbon directly covalently attached to the amino group being identified as the 4-position carbon. Consequently, references herein to R,R monatin, S,S monatin, R,S monatin, and S,R monatin mean: 2R,4R monatin, 2S,4S monatin, 2R,4S monatin, and 2S,4R monatin, respectively, unless otherwise indicated.
It should be noted that in the literature, the monatin carbon backbone has also been numbered using an alternative convention, with the carbon attached to the alcohol group being the 4-position carbon, and the carbon attached to the amino group being the 2-position carbon. Accordingly, for example, references to 2S,4R monatin in this disclosure would be the same as references to 2R,4S monatin in literature using the alternative numbering convention.
Furthermore, because of various naming conventions, monatin is known by a number of alternative chemical names, including: 2-hydroxy-2-(indol-3-ylmethyl)-4-aminoglutaric acid; 4-amino-2-hydroxy-2-(1H-indol-3-ylmethyl)-pentanedioic acid; 4-hydroxy-4-(3-indolylmethyl)glutamic acid; and, 3-(1-amino-1,3-dicarboxy-3-hydroxy-but-4-yl)indole.
At least in part because of its sweetening characteristic, it would be desirable to have an economic source of monatin. Certain isomeric forms of monatin can be found in the bark of roots of the Schlerochiton ilicifolius plant located in the Transvaal Region of South Africa. However, the concentration of the monatin present in the dried bark, expressed as the indole in its acid form, has been found to be about 0.007% by mass. See U.S. Pat. No. 4,975,298. Further, the method by which monatin is produced in the plant is presently unknown. U.S. patent application Ser. No. 10/422,366 (“the '366 application”), on the other hand, which is hereby incorporated by reference, discloses, inter alia, polypeptides, pathways, and microorganisms for in vivo and in vitro production of monatin.